(CNN) -- With a new poll showing their race in a virtual dead heat nationally, the Democratic presidential candidates are making their final pitches Monday to voters before Super Tuesday.

Sens. Hillary Clinton and Barack Obama made campaign swings in the Northeast as nearly two dozen states get ready to hold contests in what will virtually be a national primary.

At a roundtable discussion in New Haven, Connecticut, Clinton returned to two issues she repeatedly has touched on, health care and the economic concerns of the middle class.

"Most Americans are in-between people," she said. "You know, the middle class is under tremendous pressure. It is everything. The cost of everything is going up. And even if you make what used to be considered good wages, they don't cover the increase in costs, in everything from energy to health care." Watch Clinton stump for votes »

During the roundtable discussion at Yale University, Clinton became teary-eyed -- a moment that harkened back to her much talked-about display of emotion on the eve of the New Hampshire primary -- when she was introduced by Penn Rhodeen, a public interest lawyer who worked with Clinton when she was in college. Watch Clinton get personal »

Obama on Monday emphasized his ability to attract independents and Republicans in an appearance in East Rutherford, New Jersey, home of the new Super Bowl champions, the New York Giants.

Obama was introduced by actor Robert De Niro and joined on stage by Sen. Edward Kennedy. Kennedy is a Massachusetts Democrat and a fan of the New England Patriots, the team the Giants beat Sunday night.

"I have said repeatedly that this campaign is about bringing people together. And for me to be able to bring a Patriots fan to the Meadowlands the day after the Super Bowl is like bringing the lion and the lamb together," Obama said. "We can bridge all gaps and all divisions in this country."

Super Tuesday

Live from the CNN Election Center, the best political team covers every race 40 hours nonstop.Tuesday, beginning 6 a.m. ET

The senator from Illinois also said he would be the best candidate to beat Sen. John McCain of Arizona, the emerging front-runner in the GOP presidential race, because of his early opposition to the Iraq war.

Obama has criticized Clinton for voting for the 2002 resolution that authorized President Bush to use force against Iraq to enforce U.N. sanctions.

"When I'm debating John McCain, he won't be able to say, 'Well, you supported the war, too' because I didn't," Obama said.

As the candidates made a last-minute push, a CNN/Opinion Research Corp. poll out Monday showed Obama erasing Clinton's lead among Democrats nationally. The two are in a virtual tie, with Obama at 49 percent and Clinton at 46 percent, the poll found. View poll results »

With a sampling error of plus or minus 4.5 percentage points, that margin is too close to say which Democrat is leading.

Don't Miss

The survey represents a dramatic turnaround in the race from a few months ago, when Clinton had a significant edge over Obama.

In a January 14-17 CNN/Opinion Research poll, Clinton led Obama 42 percent to 33 percent. That poll also had a margin of error of plus or minus 4.5 percentage points.

A national "poll of polls" calculated by CNN that averages five national polls finds Clinton ahead of Obama by two percentage points -- 45 percent to 43 percent. Those five surveys were done by CNN/Opinion Research, Gallup, Pew, ABC and CBS.

These findings come a day before 22 states and American Samoa hold Democratic primaries or caucuses, including large states such as California, New York and Illinois. Voters will determine how more than 40 percent of the national convention delegates, 1,681, will be allocated. That figure is fewer than 400 shy of the 2,025 needed to clinch the nomination. Watch how the delegates will be assigned »

"It's huge because there's never been this many delegates at stake, and it's coast to coast," said Time magazine's Mark Halperin. "You've got a contest in Alaska. You've got a contest in Georgia. The candidates can't even go to every state that's voting, let alone spend the kind of quality time they'd like to." View what is at stake on Super Tuesday »

Former Senate Majority Leader Tom Daschle, national co-chair of Obama's campaign, said Monday his candidate would benefit from an extended primary fight and is ready to compete in the primaries after Tuesday.

"The longer this goes, we think the better it serves our campaign," Daschle said. "We can't wait for the primaries of Maryland, Virginia [and Washington, D.C]. We look forward to the primary in Texas as well as in Ohio."

Obama has not only caught up to Clinton in national surveys but also in California, the most populous state.

A Field Research Corp. poll released Sunday shows Clinton with a statistically insignificant lead of two percentage points over Obama, 36 percent to 34 percent, in the state. Eighteen percent of California Democrats have yet to make up their minds, the survey found.

Most polls two weeks ago showed Clinton with a double-digit lead there. The latest poll's margin of error is 4.5 percentage points. Watch how California could sway the race »

Obama's California campaign received a boost Sunday when the state's first lady, Maria Shriver, endorsed the Illinois Democrat. Shriver's husband, Gov. Arnold Schwarzenegger, is backing McCain in the GOP race.

"Coming out of his overwhelming victory in South Carolina and followed quickly by his Kennedy family endorsements, Obama clearly has the momentum in this campaign," said Bill Schneider, CNN's senior political analyst.

With voters going to the polls across the country Tuesday, the Democratic candidates are pouring millions into television advertising.

As part of its advertising blitz, the Obama campaign ran a commercial during Sunday night's Super Bowl emphasizing a message of change.

Later Monday, Clinton headed to Worcester, Massachusetts. In her home state of New York, she'll participate in a town hall sponsored by the Hallmark Channel and also is expected to appear Monday evening on the "Late Show With David Letterman."

Obama is attending a rally in Hartford, Connecticut, before ending with another in Boston, Massachusetts.

The candidates' spouses will be in the West. Former President Clinton will hold three events in California, while Michelle Obama will attend a rally Monday night in Tucson, Arizona. E-mail to a friend